The present disclosure relates to inkjet printing, and more particularly toward an inkjet printhead useful in ejecting non-water-based inks in an imagewise fashion.
A typical inkjet printer supplies ink to create a printed image through inkjets that are part of jet stacks. A jet stack is a stack of etched plates that are brazed together having etched cavities that are aligned to form numerous ink passageways and manifolds that feed ink to inkjet apertures etched on a face of the jet stack. To feed the numerous individual jets, a jet stack normally includes a main manifold that runs across a length of the jet stack (x-direction). Numerous smaller manifolds, called finger manifolds, feed a y-direction distribution of jets. The finger manifolds ensure that proper mass flow is maintained to the individual jets.
The word “printer” as used herein encompasses any apparatus, such as digital copier, bookmaking machine, facsimile machine, multi-function machine, etc. that performs a print outputting function for any purpose.
Some inkjet printers, such as those that use melted solid ink, must have their printheads purged after warming the supply of solid ink. A warming cycle melts both the ink supply in preparation for its use and melts any residual ink left in the printhead. Melted ink is then purged from the printhead by applying a flow of melted ink to the printhead. Purging the ink through all of the ink-jets ensures a proper mass flow is available to each ink-jet.
FIG. 1 is a wire frame perspective view of typical finger manifold 20. The longitudinal manifold 20 includes an entrance 22 at a first end 24, a filter 26 on a first side 28 and a purge vent 30 at a second end 32. The purge vent 30 is located on a second side 34 opposite the first side 28. Arrows 36 show a typical laminar flow of ink through the finger manifold 20 during a purge. The ink flows into the manifold 20 from the entrance 22 and then out past through the filter 26 to inlets 38 that lead to the inkjet apertures not shown in this drawing.
The filter 26 prevents contamination of the inkjets by filtering unwanted particulates from entering the inlets 38. The filter 26 is a perforated thin plate with holes smaller than the inlets 38.
Large scale bubbles that may enter the finger manifold 20 during purging cannot go through the filter 26 because the holes that are smaller than the bubble are so numerous that the flow will simply go around a bubble instead of dragging the bubble through the filter 26. Also, pressure cannot be increased enough to merely push the bubble through the filter 26 because components of the finger manifold 20 are so thin that they may be damaged by too much ink pressure.
The purge vent 30 does provide a significant enough pressure drop to allow a bubble to exit. The laminar flow 36 of ink entering the manifold 20 then pushes the bubble to the purge vent 30.
The finger manifold 20 may be oriented so that the first end 24 and entrance 22 becomes even vertically higher than the second end 32, as shown in the cross-section view of the finger manifold 20 in FIG. 2. Streamlines 36 show that ink entering near manifold 20 closer to the second side 34 vents out of the purge vent 30. The laminar flow 36, however, splits at location 40 which results in the flow 36 forcing a bubble 42 to remain trapped in the manifold 20 at the second end 32. This trapped bubble 42 may cause problems with acoustic resonance in the ink flow resulting in misfiring or non-firing of inkjets. Further the bubble may take hours to dissolve.
Also, with this tilted orientation, a bubble 44 remaining in the finger manifold 20 gets trapped in the corner 46 at the first end 24 due to the buoyancy of the bubble. As shown, the laminar flow 36 of the ink does not dislodge bubble 44 from this corner. Similarly, the bubble 44 may cause problems with ink flow resulting reduced performance of the printer.